NJ here.
Yes, our bump stock ban is probably worded as such that it would include FRTs. No manufacturer or retailer I've seen will ship one here. You could probably buy one in PA, but nobody wants to be the guinea pig dragged through the courts for good reason. You'd have nowhere to shoot it regardless.
In addition to this, hanging some old blankets surrounding your test area may be of marginal help, the thicker the better.